Unique oblique lighting technique using a brightfield darkfield objective and imaging method relating thereto

ABSTRACT

A process is provided for imaging a surface of a specimen with an imaging system that employs a BD objective having a darkfield channel and a bright field channel, the BD objective having a circumference. The specimen is obliquely illuminated through the darkfield channel with a first arced illuminating light that obliquely illuminates the specimen through a first arc of the circumference. The first arced illuminating light reflecting off of the surface of the specimen is recorded as a first image of the specimen from the first arced illuminating light reflecting off the surface of the specimen, and a processor generates a 3D topography of the specimen by processing the first image through a topographical imaging technique. Imaging apparatus is also provided as are further process steps for other embodiments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/561,541, filed Sep. 5, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/518,937, filed Apr. 13, 2017, now U.S. Pat. No.10,437,034, issued Oct. 8, 2019, which is a National Stage ofPCT/US2015/055283, filed Oct. 13, 2015, which claims the priority toU.S. Provisional Patent Application No. 62/063,564, filed Oct. 14, 2014,which are incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention generally relates to imaging techniques andapparatus. In particular embodiments, it relates to topographicalimaging techniques. In particular embodiments, it relates to imagingapparatus employing brightfield/darkfield objective, and improvements tosuch apparatus by employing a light barrier in the darkfield channel.

BACKGROUND OF THE INVENTION

Standard techniques for creating 3D topographies include stylusinstruments, profilometers, ultrasonic transducers, and lasertriangulation among others. Shape-from-shading (SFS) and photometricstereo (PMS) have been used to create topographies by illuminating aspecimen 1 with one or more a light sources 2, 3 directing oblique light4, 5 toward the specimen 1 at an angle from 5 to 85 degrees and moretypically from 25 to 75 degrees, as generally represented in FIG. 1 .The oblique illumination is reflected from the surface S of the objectas reflected light 6, and is captured by an image sensor (not shown)such as a CCD or CMOS sensor of a digital camera 7. The light sourcesare moved to different positions located circumferentially around theobject, with images taken at these different positions. These images areused to calculate the topography of the specimen 1 by known means,employing appropriate processor(s) 8.

A standard reflected light microscope employing brightfield anddarkfield functionality is shown in FIGS. 2 and 3 . In this example themicroscope 10 is equipped with a camera 12. Oculars may also be present,such that the numeral 12 is to broadly represent oculars and/or acamera. Although the following description will refer to a reflectedlight microscope, similar techniques apply to transmitted lightmicroscopes or instruments using brightfield/darkfield microscopeobjectives. A reflected light microscope 10 will be referenced in thefollowing descriptions but the technology may apply to any imagingsystem using a brightfield/darkfield objective. The systems generallyconsist of a light source 14 providing light 24, a vertical illuminator16, a brightfield/darkfield (BD) switch 18 and a BD objective 20. U.S.Pat. Nos. 3,930,713 and 4,687,304 describe a BD objective. In a standardBD objective 20, two channels are provided to guide the light to thespecimen 1. The light 24 is directed to a mirror 25 that reflects thelight 24 toward the specimen 1 downwardly through the verticalilluminator 16, the nosepiece 28, and BD objective 20. The BD switch 18,as schematically shown, serves to limit the light 24 to pass either intoa brightfield channel 22 or darkfield channel 26 separated by a shieldwall 21. With the BD switch 18 in a bright field position as in FIG. 2 ,the light 24 is limited to a beam that is reflected off of the mirror 25to enter the brightfield channel 22, which directs the illuminatinglight 24′ through the BD objective 20 toward the surface S of thespecimen 1 at an angle perpendicular (90 degrees) to the plane of thespecimen 1 and allows the reflected light 30 to pass to the oculars orcamera 12. As seen in FIG. 3 , when the BD switch 18 is in a darkfieldposition the light 24 is limited to an annular beam that is reflectedoff of the mirror 25 to enter the darkfield channel 26, which is anannular channel directing illuminating light 24″ toward the specimen atan angle less than 90 degrees and typically 25 to 75 degrees.

It can be seen in FIG. 2 that the light path in brightfield(illuminating light 24′) is projected through the center of thenosepiece 28 and through the brightfield channel 22 of the BD objective20. The reflected light 30 is reflected back through the brightfieldchannel 22, through the nosepiece 28 and tube lens 32 and is affected byany oculars and/or captured by a camera 12. It is seen here that theillumination light 24′ in brightfield is at 90 degrees to the surface Sof the specimen 1 and the reflected light 30 that is measured travelsparallel to the illumination light 24′ but in an opposite direction. Theprojected illuminating light 24′ illuminates the entire field of view.

FIG. 3 shows the microscope 10 in darkfield mode. Here the light 24 isblocked by the darkfield switch 18 so that no light passes through thebrightfield channel 22 and is instead directed to pass through thedarkfield channel 26 as illuminating light 24″. This produces an annularbeam (or, in other terms, a hollow cylinder or annular cylinder) oflight that is projected toward the specimen 1 at an oblique angledetermined by the design of the objective 20 and wall of the darkfieldchannel 26. As known, the BD objective will have mirrors and/or prismsand/or light diffusers built into the objective to direct the obliquelight. The illuminating light 24″ reflects off the surface S of thespecimen 1 and the reflected light 30 travels up the brightfield channelto the ocular or camera 12. The projected darkfield illuminating light24″ illuminates the entire field of view from about the entire periphery(360 degrees) of the objective.

In brightfield imaging it can be seen that the field of view F, whichtakes in at least a portion of the specimen 1, is filled by direct 90degrees illumination (the incoming illuminating light 24′ is orthogonalto the general resting plane of the specimen 1) whereas in darkfieldimaging, the field of view F is filled by oblique illumination (theincoming illuminating light 24″ is at an oblique angle to the generalresting plane of the specimen 1). The darkfield illumination is evenlydistributed through the 360 degree circumference of the BD objective 20.

SUMMARY OF THE INVENTION

In a first embodiment, the present invention provides a process forimaging a surface of a specimen with an imaging system that employs a BDobjective having a darkfield channel and a bright field channel, the BDobjective having a circumference, the process including the steps of:obliquely illuminating the specimen through the darkfield channel with afirst arced illuminating light that obliquely illuminates the specimenthrough a first arc of the circumference, said first arced illuminatinglight reflecting off of the surface of the specimen; recording a firstimage of the specimen from the first arced illuminating light reflectingoff the surface of the specimen; and generating a 3D topography of thespecimen by processing the first image through a topographical imagingtechnique.

In a second embodiment, the present invention provides an imaging systemas in any of the forgoing embodiments, wherein the first arc is from 1degree or more to 180 degrees or less.

In a third embodiment the present invention provides an imaging systemas in any of the forgoing embodiments, wherein the first arc is from 2degrees or more to 5 degrees or less.

In a fourth embodiment, the present invention provides an imaging systemas in any of the forgoing embodiments, further including the step of:obliquely illuminating the specimen through the darkfield channel with asecond arced illuminating light that obliquely illuminates the specimenthrough a second arc of the circumference different from said first arc,said second arced illuminating light reflecting off of the surface ofthe specimen; and recording a second image of the specimen from thesecond arced illuminating light reflecting off the surface of thespecimen, wherein said step of generating a 3D topography includesprocessing the second image through a topographical imaging technique.

In a fifth embodiment, the present invention provides an imaging systemas in any of the forgoing embodiments, wherein all said obliquelyilluminating steps include: providing a light barrier in the darkfieldchannel, the light barrier having a body that does not permit thepassage of light therethrough, and a darkfield opening in the body thatdoes permit the passage of light therethrough, and deliveringilluminating light into the darkfield channel to the light barrier andthrough the darkfield opening to provide the arced illuminating lightthat obliquely illuminates the specimen.

In a sixth embodiment, the present invention provides an imaging systemas in any of the forgoing embodiments, including a processor controlsthe oblique illumination of any said oblique illumination step andcontrolling any said image recording step.

In a seventh embodiment, the present invention provides an imagingsystem as in any of the forgoing embodiments, wherein the processorcontrols said step of generating a 3D topography.

In an eighth embodiment, the present invention provides an imagingsystem as in any of the forgoing embodiments, including the step of:orthogonally illuminating the specimen through the brightfield channelwith brightfield illuminating light, said brightfield illuminating lightreflecting off of the surface of the specimen; and recording a thirdimage of the specimen from the brightfield illuminating light reflectedoff the surface of the specimen, wherein said step of generating a 3Dtopography includes processing the third image through a topographicalimaging technique.

In a ninth embodiment, the present invention provides an imaging systemas in any of the forgoing embodiments, wherein the topographical imagingtechnique is selected from shape from shading techniques, photometricstereo techniques, and Fourier ptychography modulation techniques.

In a tenth embodiment, the present invention provides an improvement toan imaging apparatus for imaging a surface of a specimen, the imagingapparatus employing a BD objective having a darkfield channel and abright field channel, the BD objective having a circumference. Theimprovement includes placing a light barrier in the darkfield channel,the light barrier having a body that does not permit the passage oflight therethrough, and a darkfield opening in the body that does permitthe passage of light therethrough, such that the body blocksilluminating light traveling through the darkfield channel toward thespecimen. The opening defines a passage for the illuminating lighttraveling through the darkfield channel toward the specimen, and thusdefines arced illuminating light that obliquely illuminates the specimenthrough the darkfield channel from a discrete direction through only anarc of the circumference.

In an eleventh embodiment, the present invention provides an imagingapparatus as in any of the forgoing embodiments, wherein said arc isfrom 1 degree or more to 180 degrees or less.

In a twelfth embodiment, the present invention provides an imagingapparatus as in any of the forgoing embodiments, wherein said arc isfrom 2 degrees or more to 5 degrees or less.

In a thirteenth embodiment, the present invention provides an imagingapparatus as in any of the forgoing embodiments, further comprising aprocessor employing topographical imaging techniques on images taken bysaid imaging apparatus.

In a fourteenth embodiment, the present invention provides an imagingapparatus as in any of the forgoing embodiments, wherein the lightbarrier rotates so as to permit the placement of said opening atvariable positions about said circumference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a prior art process andapparatus for oblique illumination of a specimen for recording by acamera;

FIG. 2 is a schematic representation of a prior artbrightfield/darkfield microscope, shown in brightfield imaging mode;

FIG. 3 is a schematic representation of a prior artbrightfield/darkfield microscope, shown in darkfield imaging mode;

FIG. 4 is a schematic representation of a brightfield/darkfieldmicroscope in accordance with this invention, shown in brightfieldimaging mode;

FIG. 5 is a schematic representation of a brightfield/darkfieldmicroscope in accordance with this invention, shown in darkfield imagingmode;

FIG. 6 is a top plan view of an embodiment of a light barrier of thisinvention;

FIG. 7 is a side view of an embodiment of a light barrier of thisinvention;

FIG. 8A is a schematic representation of another embodiment of a lightbarrier of this invention, showing a plug unit providing multiple plugsto selectively cover and uncover two openings therein, with the plugmoved to uncover the opening on the left and cover the opening on theright;

FIG. 8B is a schematic representation of the embodiment of a lightbarrier of FIG. 8A, but with the plug moved to uncover the opening onthe right and cover the opening on the left;

FIG. 9A is a schematic representation of another embodiment of a lightbarrier of this invention, showing a body having multiple openingstherein, each with its own separately actuated plug, actuated to eitheropen or close its associated opening; and

FIG. 9B is a schematic representation of the light barrier embodiment ofFIG. 9A, but shown with a different opening opened by movement of anassociated plug.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention modifies a standard BD microscope or otherinstrument using a BD objective so that in brightfield the BD objectivetransmits light normally and as described above. In darkfield, the lighttransmitted through the darkfield channel is limited so that thedarkfield illumination is not through the entire 360 degreecircumference of the BD objective but rather through only a portion ofthe circumference.

With reference to FIGS. 4 and 5 a microscope employing brightfield anddarkfield functionality in accordance with this invention is shown anddesignated by the numeral 110. In this embodiment the microscope 110 isequipped with a camera 112. Oculars may also be present, such that 112is to broadly represent oculars and/or a camera. Although the followingdescription will refer to a reflected light microscope, similartechniques apply to transmitted light microscopes or other instrumentsusing BD objectives. The systems generally consist of a light source 114providing light 124, a vertical illuminator 116 (light guide), abrightfield/darkfield (BD) switch 118 and a BD objective 120. As in astandard BD objective 20, two channels are provided to guide the lightto the specimen 1. The light 124 is directed to a mirror 125 thatreflects the light 124 toward the specimen 1 downwardly through thevertical illuminator 116, the nosepiece 128, and BD objective 120.

The BD switch 118, as schematically shown, serves to limit the light 124to pass either into a brightfield channel 122 (FIG. 4 ) or darkfieldchannel 126 (FIG. 5 ) separated by a shield wall 121. With the BD switch118 in a bright field position as in FIG. 4 , the light 124 is limitedto a beam that is reflected off of the mirror 125 as illuminating light124′ to enter the brightfield channel 122, which directs theilluminating light 124′ through the BD objective 120 toward the surfaceS of the specimen 1 at an angle perpendicular (90 degrees) to the planeof the specimen 1 and allows the reflected light 130 to pass to theoculars or camera 112. As seen in FIG. 5A, when the BD switch 118 is ina darkfield position the light 124 is limited to an annular beam that isreflected off of the mirror 125 to enter the darkfield channel 126,which is an annular channel directing light coming therethrough towardthe specimen at an angle less than 90 degrees and typically 25 to 75degrees.

In some embodiments, the darkfield channel 126 directs illuminatinglight toward the specimen at an angle less than 90 degrees, in otherembodiments, less than 80 degrees, in other embodiments, less than 70degrees, in other embodiments, less than 80 degrees, in otherembodiments, less than 70 degrees, in other embodiments, less than 60degrees, in other embodiments, less than 50 degrees, in otherembodiments, less than 40 degrees, and, in other embodiments, less than30 degrees. In some embodiments, the darkfield channel 126 directsilluminating light toward the specimen at an angle greater than 20degrees, in other embodiments, greater than 30 degrees, in otherembodiments, greater than 40 degrees, and in other embodiments, greaterthan 50 degrees.

The distance between the distal end of the objective and the specimen isknown as the working distance (see FIG. 5A). In some embodiments, theworking distance is from 0.05 mm or more to 40 mm or less. In someembodiments, the working distance is from 0.7 mm or more to 30 mm orless, and, in other embodiments, from 1 mm or more to 25 mm or less mm.In some embodiments, the working distance is 10 mm or less, in otherembodiments, 5 mm or less, in other embodiments, 3 mm or less, in otherembodiment, 2 mm or less, in other embodiments, 1.5 mm or less and, inother embodiments, 1 mm or less.

In some embodiments, the field of view of the BD objective 20 is lessthan 10 mm. In some embodiments, the field of view of the BD objectiveis less than 5 mm, in other embodiments, less than 2 mm, in otherembodiments, less than 1 mm, in other embodiments, less than 500 μm, inother embodiments, less than 200 μm, in other embodiments, less than 100μm, in other embodiments, less than 50 μm.

When viewing a microscopic specimen at, for example, a size of less than10 μm, the distance of the microscope objective is often less than 5 mmfrom the surface of the specimen depending on the working distance ofthe objective. For example a typical working distance, WD, of a 50×objective is less than 2 mm and, for a 100× objective, is typically 1 mmor less. The physical outside diameter of an objective is typicallybetween 20 and 50 mm. By way of example, with a 20 mm diameter specimenand 5 mm WD, the angle of the light projecting off the surface would beapproximately 26 degrees. In the more likely case of a WD of 1 mm theangle of light projecting on the specimen would be 6 degrees.Photometric stereo optimally uses illumination at 30 to 80 degrees. Inmost microscope use cases, then, it would not be possible to determinetopographies of specimens using photometric stereo or other imagingtechniques requiring oblique lighting due to the low incident of obliqueillumination.

The present invention uses the darkfield channel of the objective todirect the light onto the surface of the specimen. This allows the lightsource to be much closer to the vertical axis of illumination. In theabove standard illumination the light had to be outside the radius ofthe objective. The use of the darkfield channel allows the light sourceto be within the radius of the specimen and essentially be adjacent tothe light path. The distance from the vertical axis can now beapproximately equal to the WD allowing an angle of illumination to be 45degrees. This angle may vary slightly with the design of the objectivebut is typically in the range of 25 to 75 degrees. Thus, the imagingsystems according to this invention achieve oblique illumination anglesdespite the very tight working distances required in many applications.The method taught herein can be used to determine topographies inmicroscopy applications that could not be achieved by standard methods.

It can be seen in FIG. 4 that the light path in brightfield(illuminating light 124′) is projected through the center of thenosepiece 128 and through the brightfield channel 122 of the BDobjective 120. The reflected light 130 is reflected back through thebrightfield channel 122, through the nosepiece 128 and tube lens 132 andis affected by any oculars and/or captured by a camera 112. It is seenhere that the illumination light 124′ in brightfield is at 90 degrees tothe general resting plane of the specimen 1 and the reflected light 130that is measured travels parallel to the illumination light 124′ but inan opposite direction. FIG. 4B shows a schematic cross sectional view ofthe specimen 1 and the brightfield illumination light 124′ that isprojected onto the specimen 1. The projected brightfield illuminationlight 124′ illuminates the entire field of view.

FIG. 5 shows the microscope 110 in darkfield mode. Here the light 124 isblocked by the darkfield switch 118 so that no light passes through thebrightfield channel 122 and is instead directed to pass through thedarkfield channel 126 as illuminating light 124″. As with the embodimentof FIG. 3 of the prior art, this blocking of the light 124 produces anannular beam (or, in other terms, a hollow cylinder or annular cylinder)of light reflected off of mirror 125 and projected toward the specimen1. However, in distinction over the prior art, the entirety of thatannular beam of illuminating light 124″ does not reach the specimen atan oblique angle determined by the design of the objective 120 and wallof the darkfield channel 126. Instead, only a portion of the light atfrom less than the entire 360 degree circumference of the BD objectiveis delivered down the darkfield channel to reach the specimen, as arcedilluminating light 124*. This arced illuminating light 124* stillilluminates the entire field of view, but, rather than doing so from theentire 360 degree circumference of the objective, does so from adiscrete direction of limited degrees (or minutes of arc), i.e., fromonly a portion of the circumference. In other embodiments, the darkfieldprojection of arced illuminating light 124* illuminates the entire fieldof view from a discrete direction of limited degrees (or minutes ofarc), and the darkfield illumination is devoid of any additionalillumination that would interfere with the surface shading caused by theobliquely introduced arced illuminating light 124*. This is accomplishedby positioning a light barrier 140 in the path of the illuminating light124″.

In some embodiments, such as that shown in FIG. 6 , the light barrier140 has a body 142 with a darkfield opening 144 therein so that unwantedilluminating light 124″ is blocked and a desired arced illuminatinglight 124* passes through the opening to be projected toward thespecimen 1 through less that the entire 360 degree circumferencepracticed in the prior art. The body 142 of the light barrier 140 doesnot let illuminating light 124″ pass through, while the darkfieldopening 144 simply defines an open path for the illuminating light 124″,which is then defined as arced illuminating light 124* after beinglimited by passage through the light barrier opening 144. The lightbarrier 140 also defines a brightfield opening 146 for the brightfieldchannel 122 and illuminating light 124′, as well as all reflected lightwhether from brightfield or darkfield illumination.

FIG. 5 shows a schematic cross sectional view of the specimen 1 and thearced of illumination light 124* that is projected onto the specimen 1.The projected arced illuminating light 124* illuminates the entire fieldof view, but at an oblique angle and from a discrete position. Withreference back to FIG. 5 , it is seen that only the left side of thedarkfield channel 126 is shown having arced illuminating light 124*traveling therethrough, as that reflects the location of the darkfieldopening 144 in the light barrier 140. The illumination thus comes fromthat direction and shines at an oblique angle across the field of view.

In some embodiments, the light barrier 140 is secured in the nosepiece128. In other embodiments, the light barrier 140 is secured in thevertical illuminator 116. It will be appreciated that the light barrier140 and concepts related herein can be implemented in other ways aswell, such as in the BD objective 120.

In some embodiments, such as that in FIG. 5A, the light barrier 140 ismounted in the nosepiece 128, and is secured to a bearing housing 148that is secured to the nosepiece 128 without intruding upon thedarkfield channel 126 and the light traveling therethrough, i.e., it isdesirable that the light be unaffected by the encroachment of thebearing housing 148 in the darkfield channel 126. The bearing housing148 includes bearings 150 permitting the rotation of the light barrier140 to position the darkfield opening 144 at a desired position aboutthe circumference of the BD objective 120, thus defining the arcedilluminating light 124* projected toward the specimen 1. The rotation isvisually represented in FIG. 6 by the double-headed arrow A.

In some embodiments, a driver 152 serves to rotate the light barrier 140to place the darkfield opening 144 in a desired position. In someembodiments, the driver 152 is a motor that interacts with the lightbarrier 140 through a belt 154, but gearing and other interactions canbe employed. It will be appreciated that the driver 152 could also be amanually manipulated driver, such as a wheel or knob geared or belted orotherwise associated with the light barrier 140 to rotate it.

In some embodiments, a sensor 156 is mounted to the microscope 110 at anappropriate location to identify a zero position for the light barrier140. The sensor 156 on the microscope 110 will identify the zeroposition when the sensor aligns with a reference element 158 on thelight barrier 140. The zero position establishes a known startingposition for the light barrier 140 and more particularly the darkfieldopening 144 therein, and this known starting position is used forindexing imaging so that each image recorded by the camera 112 hasassociated with it a known lighting position relative to the specimen.

The camera can be any camera useful in imaging systems and specificallyused for imaging specimens intended for topographical analysis. Thesewill often employ a CCD or CMOS sensors.

It will be appreciated that the control of all elements of themicroscope can be implemented in known ways, typically with some or allcontrols being implemented through various hardware and/or softwareand/or firmware, all represented and designated herein as a processor170. One or more processors can be used and a myriad of hardware such asjoysticks, relays, switches among others. The processor 170 can recordthe images taken from the camera and be programmed with the appropriatealgorithms to analyze one or more images and recreate a topographicalimage of the portion of the specimen imaged.

For the topographical imaging techniques implemented by the processor170, it is typically necessary or at least helpful to have associatedwith a particular image the positioning of the incoming oblique lightrelative to the circumference of the objective. The shading created bythe oblique light is dependent upon the position of the incoming lightrelative to the circumference, and establishing a zero positionfacilitates the automation of processes for taking multiple images andcalculating topographies based upon those multiple images. Once a zeroposition is established, the processor and associate hardware and/orfirmware and/or software can carry out an automated process of providingoblique illumination from a first position about the circumference,taking an image and collecting image data and associating it with theillumination from the first position, then providing obliqueillumination from a second position about the circumference, taking animage and collecting image data and associating it with the illuminationfrom the second position positional data; repeating the process asdesired to obtain a desired number of imaging data sets from a desirednumber of illuminating positions. In some embodiments, the sensor 156 isan optical proximity sensor, wherein a light shined by the sensor 156 isblocked by a reference element 158 on the light barrier 140 when thesensor 156 and reference element 158 are aligned. In other embodiments,the sensor 156 magnetic position sensor, working by sensing a magnetserving as a reference element. Mechanical limit switches and Halleffect sensors are other examples.

In some embodiments, such as seen in FIG. 7 the light barrier 140 has aspool-like shape with two opposed walls 160, 162, with a separatingsidewall 164. A belt such as belt 154 (or gearing or other drivemechanisms) can engage the sidewall 164 to drive the light barrier 140.

In some embodiments, such as that shown in FIGS. 8A and 8B, a lightbarrier 240 has multiple openings represented at darkfield openings 244a and 244 b, but any number of openings can be employed taking intoaccount obvious size constraints. The darkfield openings 244 a, 244 bjoin to the perimeter of the of the body 242 of the light barrier sothat moveable plugs 245 a and 245 b can be employed to selectively blocka respective darkfield opening 244 a, 244 b. In the embodiment of FIG.8A the darkfield openings 244 a and 244 b are opposite one another, andthe moveable plugs 245 a and 245 b are joined, forming a plug unit 247such that when the movable plug 245 b blocks darkfield opening 244 b,the movable plug 245 a is removed from darkfield opening 244 a (as inFIG. 8A) and vice versa (as in FIG. 8B). This allows light to passthrough a desired darkfield opening 244 a, 244 b, providing the arcedilluminating light 124*, and also allows for quick switching of thepositioning of the arced illuminating light 124*, by switching thepositioning of the plug unit 247. It can be appreciated that multipleslits and moveable plugs may be employed, and that each plug could haveits own control as opposed to the common control established in thepresent exemplary embodiment of FIGS. 8A and 8B.

In another embodiment, such as that shown in FIGS. 9A and 9B, a lightbarrier 340 has six darkfield openings 344 a, 344 b, 344 c, 344 d, 344e, and 344 f spaced at 60 degrees apart around the circumference of thebody 242 of the light barrier. Any number and position desired couldalternatively be employed. The darkfield openings 344 a-f join to theperimeter of the of the body 342 of the light barrier 340 so thatmoveable plugs 345 a, 345 b, 345 c, 345 d, 345 e, and 345 f can beemployed to selectively block a respective darkfield opening 344 a-f. Inthis embodiment, the movable plugs 345 a-f each can be actuatedindependently to block a respective opening. To visually represent theselective movement, plug 345 a is shown removed from its opening 344 ain FIG. 9A, with all other plugs seated to block their respectiveopenings, while, in FIG. 9B, plug 345 b is shown removed from itsopening 344 b, with all other plugs seated to block their respectiveopenings.

In some embodiments, such plugs can be moved by linear actuators,solenoid, eccentric, or any other known method of motion control. Linearactuators 349 a, 349 b, 349 c, 349 d, 349 f are employed.

In any embodiment, the size of the arced illuminating light 124* mayvary as desired based on results achieved and results desired. Thisentails a choice of the sizing of the darkfield opening 144 (or 244 a,244 b) In some embodiments, the arced illuminating light 124* rangesfrom 1 degree or more to 180 degrees or less (60 or more to 10,800 orless minutes of arc). In other embodiments, the arced illuminating light124* ranges from 45 degrees or more to 120 degrees or less (2,700 ormore to 7,200 or less minutes of arc), in other embodiments, from 30degrees or more to 45 degrees or less (1,800 or more to 2,700 or lessminutes of arc), in other embodiments, from 10 degrees or more to 30degrees or less (600 or more to 1,800 or less minutes of arc), in otherembodiments, from 5 degrees or more to 10 degrees or less (300 or moreto 600 or less minutes of arc), and, in other embodiments, from 2degrees or more to 5 degrees or less (120 or more to 300 or less minutesof arc). The size of the arced illuminating light is dependent upon thesize of the darkfield opening 144 relative to the arc of the annulardarkfield channel 126 with which it communicates.

Another aspect of the invention is to use the oblique lighting BDmicroscopes described above to create a 3D topography by taking multipleimages of a specimen 1 obliquely illuminated with arced illuminatinglight 124* from different positions about the 360 circumference of theBD objective 120 using the light barrier 140, and processing the datafrom those images in accordance with topographical imaging techniques.The choice of topographical imaging technique is not limited to anyparticular technique, but, in some embodiments, is selected from shapefrom shading techniques, photometric stereo techniques, and Fourierptychography modulation techniques. The processor 170 receives theimaging data from the camera 112 and is programmed through one or moretopographical imaging techniques to generate data used to create atopographical representation of the area of the specimen 1 that wasimaged. This is represented at output 172. Using known techniques suchas shape from shading algorithms, photometric stereo algorithms, andFourier ptychography modulation algorithms with the know size, number,and position of the arced illuminating light, the angle of the obliqueillumination, a 3D topography can be generated.

In some topographical imaging techniques such as shape from shading(SFS), a single obliquely illuminated specimen image generated fromarced illuminating light at a single position can be sufficient togenerate topographical data and images. In other topographical imagingtechniques such as photometric stereo, at least two obliquelyilluminated specimen images generated from arced illuminating light attwo positions can be sufficient to generate topographical data andimages. In other topographical imaging techniques such as Fourierptychography modulation, at least two obliquely illuminated specimenimages generated from arced illuminating light at two positions plus animage from brightfield illumination is needed to generate topographicaldata, and 10 or more obliquely illuminated specimen images will provideeven better data for Fourier ptychography modulation. The existingalgorithms and algorithms yet to be developed in this field will providethe ordinarily skilled artisan with the knowledge as to the number oftype of images needed. The present invention does not invent or alterthe algorithms but rather provides methods and apparatus that allows fortheir implementation.

It will be appreciated that, in some embodiments, the processor 170(which again, represents any number of appropriate processors, hardware,software, firmware), automates the control of the light barrier, theillumination, the image collection and generation of topographical dataand/or images.

Thus this invention provides a process for imaging a specimen with animaging system that employs a BD objective having a darkfield channeland a bright field channel and defining a circumference about thespecimen to be imaged. The process includes obliquely illuminating thespecimen through the darkfield channel with a first arced illuminatinglight that obliquely illuminates the specimen through a first arc of thecircumference, and taking a first image providing a first image data setof the specimen from the first arced illuminating light reflected offthe surface of the specimen. In some embodiments, the process furtherincludes generating a 3D topography of the specimen by processing thefirst data through a topographical imaging technique. In someembodiments, the arc sizes are selected as described above for the arcedilluminating light 124*.

In other embodiments, the process includes, obliquely illuminating thespecimen through the darkfield channel with a second arced illuminatinglight that obliquely illuminates the specimen through a second arc ofthe circumference of the BD objective different from said first arc, andtaking a second image providing a second image data set of the specimenfrom the second arced of illuminating light reflected off the surface ofthe specimen. In other embodiments, the process further includesilluminating the specimen through the brightfield channel withbrightfield illuminating light, and taking a third image of the specimenfrom the brightfield illuminating light reflected off the surface of thespecimen. In other embodiments, the process further includes repeatingsaid obliquely illuminating step and said taking an image step for any nnumber of images producing n number of image data sets. In otherembodiments, n is from 2 to 12, in other embodiments, from 3 to 9, inother embodiments, from 4 to 7, and in other embodiments, 6.

In other embodiments, said obliquely illuminating steps includeproviding a light barrier in the darkfield channel, the light barrierhaving a body that does not permit the passage of light therethrough,and a darkfield opening in the body that does permit the passage oflight therethrough, and delivering illuminating light into the darkfieldchannel to the light barrier and through the darkfield opening toprovide the arced illuminating light that obliquely illuminates thespecimen.

In other embodiments, the process includes a processor and associatehardware and/or firmware and/or software controlling the obliqueillumination of any said oblique illumination step and controlling anysaid image taking step. In other embodiment a same or differentprocessor and associate hardware and/or firmware and/or softwarecontrols said step of generating a 3D topography.

In some embodiments, the light barrier 140 may remain stationary toallow an image to be captured from a single position. In someembodiments, the light barrier 140 may be rotated to allow multipleimages to be captured at known, specific positions of the darkfieldopening 144. In some embodiments, the light barrier (such as lightbarrier 240) will have multiple openings and plugs, with the plugssequentially manipulated to open a pathway for the arced illuminatinglight 124*. In some embodiments, the positions are generally symmetricalsuch as two images captured 180 degrees apart; three images captured at120 degrees apart, six images captured at 60 degrees apart, and so on.It will be appreciated that these measurements would have the mid-pointof each arc of each arced illumination as a reference point, with themeasurement made from mid-point to mid-point. It should be appreciatedthat the invention allows one or more images to be captured using thedarkfield oblique light and still allows a brightfield image to becaptured at 90 degrees.

In light of the foregoing, it should be appreciated that the presentinvention significantly advances the art by providing an imaging systemand topographical imaging method that is structurally and functionallyimproved in a number of ways. While particular embodiments of theinvention have been disclosed in detail herein, it should be appreciatedthat the invention is not limited thereto or thereby inasmuch asvariations on the invention herein will be readily appreciated by thoseof ordinary skill in the art. The scope of the invention shall beappreciated from the claims that follow.

The invention claimed is:
 1. An imaging apparatus for imaging a surfaceof a specimen, the imaging apparatus comprising: a microscope selectedfrom reflected light microscopes and transmitted light microscopes, themicroscope including: a brightfield/darkfield (BD) objective having adarkfield channel and a brightfield channel, the BD objective having acircumference; and a light barrier positioned in a nosepiece of themicroscope and outside the BD objective, the light barrier comprising abody that selectively permits passage of light therethrough, the lightbarrier comprising a darkfield opening that defines a passage forilluminating light traveling through the darkfield channel toward thespecimen, such that the illuminating light does not pass through anentire circumference of the BD objective.
 2. The imaging apparatus ofclaim 1, wherein the darkfield opening defines arced illuminating lightthat obliquely illuminates the specimen through the darkfield channelfrom a discrete direction throughout only an arc of a circumference ofthe BD objective.
 3. The imaging apparatus of claim 2, wherein thenosepiece is coupled with a bearing housing that is secured to thenosepiece of the microscope.
 4. The imaging apparatus of claim 3,wherein the bearing housing comprises a plurality of bearings permittingrotation of the light barrier to position the darkfield opening at adesired position about a circumference of the BD objective.
 5. Theimaging apparatus of claim 4, wherein the arc is from 1 degree or moreto 180 degrees or less.
 6. The imaging apparatus of claim 4, wherein thearc is from 2 degrees or more to 5 degrees or less.
 7. The imagingapparatus of claim 1, wherein the light barrier does not intrude uponthe darkfield channel.
 8. The imaging apparatus of claim 1, furthercomprising: a camera configured to record a first image of the specimenfrom a first arced illuminating light reflecting off the surface of thespecimen, wherein the first arced illuminating light reflecting off thesurface of the specimen is reflected back through the brightfieldchannel.
 9. The imaging apparatus of claim 8, further comprising: acomputing device in communication with the camera, the computing deviceconfigured to generate a 3D topography of the specimen by processing thefirst image through a topographical imaging technique, whereintopographical data are generated from the first image.
 10. A method forimaging a surface of a specimen with an imaging system that employs amicroscope selected from a reflected light microscope and a transmittedlight microscope including a brightfield/darkfield (BD) objective havinga darkfield channel and a brightfield channel, the BD objective having acircumference, the method comprising: rotating a light barrier to afirst position, the light barrier positioned in a nosepiece of thereflected light microscope and outside the BD objective; and obliquelyilluminating the specimen through the darkfield channel with a firstarced illuminating light that obliquely illuminates the specimen througha first arc of the circumference as defined by the light barrier in thefirst position, said first arced illuminating light reflecting off ofthe surface of the specimen, by: delivering illuminating light into thedarkfield channel to the light barrier and through a darkfield openingto provide the first arced illuminating light that obliquely illuminatesthe specimen; and recording a first image of the specimen from the firstarced illuminating light reflecting off the surface of the specimen,wherein the first arced illuminating light reflecting off the surface ofthe specimen is reflected back through the brightfield channel andrecorded as the first image.
 11. The method of claim 10, furthercomprising: generating a 3D topography of the specimen by processing thefirst image through a topographical imaging technique, whereintopographical data is generated from the first image.
 12. The method ofclaim 10 wherein rotating the light barrier positioned in the nosepieceof the reflected light microscope, comprises: rotating a bearing housingconfigured to couple the nosepiece to the microscope.
 13. The method ofclaim 12, wherein the bearing housing comprises a plurality of bearingspermitting rotation of the light barrier to position the darkfieldopening at a desired position about a circumference of the BD objective.14. The method of claim 10, wherein the darkfield opening defines arcedilluminating light that obliquely illuminates the specimen through thedarkfield channel from a discrete direction throughout only an arc of acircumference of the BD objective.
 15. The method of claim 14 whereinrotating the light barrier positioned in the nosepiece of the reflectedlight microscope, comprises: rotating the light barrier such that thearc is from 1 degree or more to 180 degrees or less.
 16. The method ofclaim 14 wherein rotating the light barrier positioned in the nosepieceof the reflected light microscope, comprises: rotating the light barriersuch that the arc is from 2 degrees or more to 5 degrees or less. 17.The method of claim 10, further comprising: rotating the light barrierto a second position; obliquely illuminating the specimen through thedarkfield channel with a second arced illuminating light that obliquelyilluminates the specimen through a second arc of the circumferencedifferent from said first arc as defined by the light barrier positionedin the second position, said second arced illuminating light reflectingoff of the surface of the specimen; and recording a second image of thespecimen from the second arced illuminating light reflecting off thesurface of the specimen, wherein the first arced illuminating lightreflecting off the surface of the specimen is reflected back through thebrightfield channel and recorded as the second image.
 18. A microscopefor analyzing a specimen comprising: a brightfield/darkfield (BD)objective having a darkfield channel and a brightfield channel, the BDobjective having a circumference; and a light barrier positioned in anosepiece of the microscope and outside the BD objective, the lightbarrier comprising a body that selectively permits passage of lighttherethrough, the light barrier comprising a darkfield opening thatdefines a passage for illuminating light traveling through the darkfieldchannel toward the specimen, such that the illuminating light does notpass through an entire circumference of the BD objective.
 19. Themicroscope of claim 18, wherein the nosepiece is coupled with a bearinghousing that is secured to the nosepiece of the microscope.
 20. Themicroscope of claim 19, wherein the bearing housing comprises aplurality of bearings permitting rotation of the light barrier toposition the darkfield opening at a desired position about acircumference of the BD objective.